Catalyst and its use for the manufacture of methane from gases containing carbon monoxide and dioxide and hydrogen

ABSTRACT

Gases of various origins which contain carbon monoxide and dioxide and hydrogen, for example the gases obtained by steam reforming or the rich gas process, refinery gases or coal gasification gases are methanized on a nickel catalyst. The object of this reaction is to obtain methane or gases which can be substituted for natural gas. To produce the catalyst, the compound Ni6Al2(OH)16.CO3.4H2O is obtained from aqueous solution. The catalyst is obtained from this compound after drying, calcination and subsequent reduction in a stream of hydrogen, whilst maintaining very specific temperature gradients between the drying stage and the calcination stage.

United States Patent 1191 Broecker et a1.

[ Oct. 14, 1975 [73] Assignee: BASF Aktiengesellschaft,

Ludwigshafen (Rhine), Germany [22] Filed: Nov. 13, 1973 21 Appl. No.2 415,292

[30] Foreign Application Priority Data Nov. 15, 1972 Germany 2255877 [52] US. Cl. 260/449.6; 208/111; 208/112; 252/455 R; 252/466 R [51] Int. Cl. C07C 27/06 [58] Field of Search 260/449 M, 449.6; 252/466 R [56] References Cited UNITED STATES PATENTS 2,151,329 3/1939 Page et a1 260/449 M 2,644,829 7/1953 Hogan 260/4496 FOREIGN PATENTS OR APPLICATIONS 820,257 9/1959 United Kingdom 260/449 M Primary Examiner.loseph E. Evans Assistant ExaminerA. Siegel Attorney, Agent, or Firm-Johnston, Keil, Thompson & Shurtleff [5 7] ABSTRACT Gases of various origins which contain carbon monoxide and dioxide and hydrogen, for example the gases obtained by steam reforming or the rich gas process, refinery gases or coal gasification gases are methanized on a nickel catalyst. The object of this reaction is to obtain methane or gases which can be substituted for natural gas. To produce the catalyst, the compound Ni Al (OI-I) .CO .4I-I O is obtained from aqueous solution. The catalyst is obtained from this compound after drying, calcination and subsequent reduction in a stream of hydrogen, whilst maintaining very specific temperature gradients between the drying stage and the calcination stage.

2 Claims, 1 Drawing Figure U.S; Patent Oct.'14,1975

CATALYST AND ITS USE FOR THE MANUFACTURE OF METHANE FROM GASES CONTAINING CARBON MONOXIDE AND DIOXIDE AND HYDROGEN The invention relates to catalysts which have been obtained by drying, calcination and reduction of specific compounds, the socalled catalyst precursors, produced in aqueous solution, or by precipitation of the catalyst precursors on supports suspended in water, and to the use of these catalysts for the manufacture of methane from gases containing carbon monoxide and dioxide and hydrogen.

The industrial cracking of preferably gaseous hydrocarbons such as, for example, methane, ethane, propane or butane on nickel catalysts in the presence of steam, to give gases essentially containing carbon monoxide and hydrogen (so-called synthesis gases) has been known for a long time. It is generally carried out at temperaturesfrom 600 to 900C. This reaction is referred to as steam reforming.

However, hydrocarbons can also be cracked at lower temperatures, again on nickel catalysts, to give gases rich in methane. The production of methane-rich gases from hydrocarbons such as ethane, propane, butane or naphtha and the like, at low temperatures is, however, an exothermic process, in contrast to steam reforming; hence, this reaction is carried out adiabatically in shaft furnaces whilst the manufacture of synthesis gases during steam reforming is carried out in tubular reactors.

German Printed Application No. 1,180,481 discloses that liquid hydrocarbons can be converted into gases rich in methane (containing more than 50% of methane after drying) by means of steam on supported nickel catalysts, at temperatures from 400 to 550C, provided certain ratios of steam to hydrocarbon are maintained during the reaction.

Conventional supported nickel catalysts are proposed, quite generally, for this process. However, it has been found that the nickel catalysts known from steam reforming at high temperatures are unsuitable for cracking hydrocarbons at low temperatures since their activity is in general inadequate because their supports have in most cases been calcined at high temperatures in order to meet the steam reforming requirements.

The alkali-free catalyst, containing of nickel on aluminum oxide, which the abovementioned Printed Application No. states to be preferred (cf. column 4, lines 29 to 49) is also rather unsuitable for the process since, if such a catalyst is to have a working life of somewhat more than 14 days, the maximum space velocities permissible are merely 0.5 kg of hydrocarbon per liter of catalyst. On the other hand, such a process is uneconomical unless space velocities of about 1 to 1.5 kg of hydrocarbon per liter of catalyst per hour are permissible (see experiments 8 and 9).

German Printed Application No. 1,227,603, by the same applicant company, states that the catalyst life in the process described in British Pat. No. 820,257 which is equivalent to the abovementioned DAS 1,180,481 is relatively short, particularly if higherboiling hydrocarbons from the boiling range of gasoline are to be cracked. This Printed Application No. proposes a supported nickel catalyst which contains, in addition to nickel and aluminum oxide, 0.75 to 8.6% of oxides, hydroxides and carbonates of alkali metals or alkaline earth metals, including magnesium.

Column 2, from line 44 onward, and column 3, up to line 16, state that optimum results are achieved when alkali metals, especially potassium, are used as catalyst additives. Consequently, potassium compounds were also used as alkalizing agents in all the examples.

The obligatory alkalization of nickel catalysts before they are used for the steam reforming of, in particular,

liquid hydrocarbons in the temperature range from 350 to 1,000C, that is to say both for the actual steam reforming process and for the production of methanerich gases, has also been proposed in ICIs German Printed Application No. 1,199,427, independently of the abovementioned applicant.

In the light of the art, as described above, there was therefore no reason why a skilled worker should propose alkali-free catalysts for the cracking of hydrocarbons since it was generally known that only nickel catalysts containing alkali were capable of preventing the deposition of carbon on the catalyst for acceptable periods of time when carrying out the reaction under economically acceptable conditions (low values of the ratio [H O] [C]).

Hence, because of the statements in German Printed Application No. 1,227,603 those skilled in the art were prejudiced against the use of alkali-free nickel catalysts for the production of rich gases since, on the one hand, the promoter action of alkalis such as, for example, potassium, was proven whilst, on the hand, only a negative result was to be expected from the use of aluminum oxide as the support (cf. Example 9 and the comparative experiments in Example 1 1 of the present application).

Those skilled in the art were similarly prejudiced with regard to the use of these catalysts in the production of practically pure methane from technical gases, containing carbon monoxide and dioxide, in a methanization stage, since it was quite generally known that the catalysts used in the cracking stage for the production of rich gases are equally suitable for use in the methanization stage (cf. in particular German Published Application No. 1,645,840).

We have now found, surprisingly, that alkali-free catalysts containing nickel and aluminum can be manufactured which are superior, when used for the production of practically pure methane from technical gases containing carbon monoxide and dioxide and hydrogen, to those known from the art (alkalized catalysts) if specific catalyst precursors produced in aqueous solution are used as the starting material for the manufacture of these catalysts, or these catalyst precursors are precipitated on supports in water and converted into the actual catalyst by precipitation, drying, calcination and reduction.

The present invention therefore relates to a catalyst which is characterized in that the compound Ni Al (OH) .CO .4H O is precipitated, as the catalyst precursor, on a support in aqueous suspension and the support together with the precipitate is separated off, dried at temperatures from to C, calcined at temperatures from 350 to 550C and subsequently reduced in a stream of hydrogen, with the proviso that between the drying stage and the calcination stage, the temperature is raised at a gradient in the range from l.66C/minute to 3.33C/minute.

The catalyst can be used for the low temperature cracking of hydrocarbons of boiling range from 30 to 300C, inthe presence of steam, to give, in particular, gases rich in methane.-

As already described in the introduction, this reac tion is exothermic and can therefore be performed adiabatically in a shaft furnace if the reactants have been preheated to a sufficiently high temperature. When mixing catalysts of the prior art, this process was generally performed by preheating the feedstocks to temperatures exceeding 350C and passing them into the catalyst bed in such a way that the bed was kept at temperatures from 400 to approx. 550C as a result of the reaction which occurs (cf. DAS 1,180,481 and DAS 1,227,603).

The catalysts of the invention now make it possible to perform the abovementioned process at lower temperatures. This is important since it is known that the methane content in the equilibrium greatly depends on the temperature and pressure; it is the higher, the lower is the selected reaction temperature and the higher is the selected pressure. When using the catalyst of the invention, it suffices merely to preheat the feedstock to temperatures above 250C. If the reaction is carried out adiabatically, the cracking can therefore be performed in the temperature range from 250C to 550C; preferably, however, it is performed in the temperature range from 300 to 450C and especially from 300 to 400C. The above data relate to the temperature to which the hydrocarbon vapor/steam mixture is preheated. This temperature depends on the raw material used and can be the lower, the lower-boiling is the hydrocarbon mixture and the higher is the proportion of paraffin in this hydrocarbon mixture.

Pressures from to 100 atmospheres gauge can be used for cracking hydrocarbons with these catalysts; preferably, pressures from 25 to 85 atmospheres gauge are chosen.

The catalysts of the invention can be exposed to 1.0 2.5 kg of naphtha/liter of catalyst per hour; preferably space velocities of 1.2 to 1.5 kg of naphtha/liter of catalyst per hour are used in industrial installations. The space velocity of course depends on the nature of the hydrocarbons. When comparing different catalysts, throughputs of 5 kg of naphtha per liter of catalyst per hour were chosen to be able to achieve appropriate effects (cf. Example 1 1) within a short time. The abovementioned space velocity however is not relevant to the industrial cracking of liquid hydrocarbons. The catalysts of the invention are capable of reliably splitting petroleum fractions of upper boiling limits extending to 300C at a space velocity of 2 kg of naphtha per liter of catalyst per hour. In the case of gasolines whose upper boiling limits are lower, higher space velocities than 2 can be employed. When cracking propane or butane, space velocities of up to 3.5 kg of naphtha per liter of catalyst per hour can be employed.

Suitable feedstocks for the low temperature cracking process are hydrocarbons of higher molecular weight than methane. Mixtures of hydrocarbons of average C number from C to C corresponding to a boiling range of about 30 to 300C, are preferred. Hydrocarbon mixtures consisting predominantly of paraffinichydrocarbons are particularly suitable. The cracking of aromatic hydrocarbons and naphthenic hydrocarbons is made more difficult than that of paraffinic hydrocarbons. However, mixtures of hydrocarbons which contain up to or aromatics and/or naphthenes can also be used. The question of whether aromatic or naphthenic hydrocarbons can be cracked depends essentially on their chemical nature.

The feedstock should contain less than 0.5 ppm of sulfur since prior art nickel catalysts, as well as the catalysts of the invention, are adversely affected by higher sulfur contents. The desulfurization process is known from the art and is usually carried out with sulfurresistant catalysts. In industrial installations, the cracking stage is usually preceded by a catalytic desulfurization stage and the hydrogen is passed over the cracking catalyst. I

The weight ratio of steam/naphtha should be not less than 0.8. In low temperature cracking using the catalysts of the invention, ratios from 1.0 to 2.0 kg of steam per kg of naphtha-are used. The use of higher ratios is not critical but is uneconomical. The amount of steam required depends on the nature of the feedstock; the preferred ratio can be lower when low-boiling hydrocarbons are used, especially if the hydrocarbons to be cracked are predominantly paraffinic.

The invention also relates to the use of the catalysts in the production of methane from gases containing carbon monoxide and dioxide and hydrogen.

It relates, in particular, to the use of the catalyst for the manufacture of methane by reaction of gases containing carbon monoxide and dioxide and hydrogen at superatmospheric pressures, the gases having been preheated to temperatures from 200 to 300C.

Preferred feedstocks for the methanization are gases as obtained in the known processes of steam cracking of hydrocarbons (steam reforming process and rich gas process). Refinery gases or gases obtained from the autothermic catalytic or non-catalytic cracking of gasolines, middle oils or heavy oils or the gasification of coal or coal derivatives are also suitable.

The catalyst of the invention can be employed for both wet methanization and dry methanization. It is preferably used for the dry methanization of rich gases since in this way it is possible to produce practically pure methane from gasoline hydrocarbons in a process which in total only comprises two stages. The rich gases from the low temperature cracking of naphtha in general contain, after drying, 50 to of methane, 19 to 25% of carbon dioxide, up to 16% of hydrogen and up to 5% of carbon monoxide. We have found that these gases can be passed over a nickel catalyst, using preheating temperatures from 200 to 300C, without causing coking of the catalyst. This was surprising since German Published Application No. 1,645,840 alleges that the post-methanization of rich gases can only be carried out in the presence of water because the nickel catalysts used for the methanization tend to coke in the absence of water. I I

The gases employed for the dry methanization are cooled to condense excess water; preferably, the gases are cooled to temperatures below 100C, for example to temperatures from 20 to C. In performing the dry methanization, it is essential that the molar ratio of hydrogen to carbon monoxide should not fall significantly below 3 since otherwise there is the danger that carbon may be deposited. This measure is not necessary in the so-called wet methanization, as described in German Published Applications Nos. 1,645,840 and 1,545,463. I

Space velocitiesfrom 2,000 to 10,000 1 (S.T.P.) of

gas per liter of catalyst per hour can be chosen for the methanization of gases. Lower space velocities are chosen at higher carbon monoxide contents in the cracked gases and conversely somewhat higher space velocities can be selected at lower carbon monoxide contents in the feedstock. Preferably, space velocities from 3,000 to 7,000 l (S.T.P.) of gas per liter of catalyst per hour are employed.

The methanization can be carried out at atmospheric pressure or superatmospheric pressure. Preferably the same pressure ranges as those employed in the manufacture of the gases are used; the preferred pressures are from 25 to 85 atmospheres gauge.

The temperature at which the methanization (dry or wet) is performed are from 200 to 300C (these data relating to the temperatures to which the dry or wet gases are preheated).

Preferably, 1M to 2M aqueous solutions of the nitrates are used to produce the catalyst precursor Ni- Al (Ol-I) .CO .4H O. The precipitant (alkali metal carbonate) is also preferably used as a IM to 2M solution. The following method has been found suitable for the production of a catalyst precursor of the abovementioned composition:

The compound Ni Al (OH) g,.CO .4H O is precipitated with alkali metal carbonates (sodium carbonate or potassium carbonate or mixtures of both) at pH values from 6.5 to 10.5, especially from 7.0 to 8.5. The starting material is an aqueous solution of the nitrates of the divalent and trivalent metals, the pH of which has been adjusted to 8 with sodium carbonate. The molar ratio Me zMe f in this solution should at least exceed 1 but should preferably be from 2.5 to 3.5; in particular, a value of 3:1 (the stoichiometric value) is chosen for the ratio of Me :Me

The catalyst precursor can be precipitated at temperatures from 0 to 100C but preferably the precipitation is effected at temperatures from 70 to 90C. Preferably, the catalyst precursor is produced by adding 2M solutions of the alkali metal carbonates to 2M mixtures of the nitrates. The precipitate formed is carefully washed until its residual alkali content is less than 0.1 or less than 0.01%, based on the dry catalyst precursor. The resulting compounds, when dried, calcined and reduced in a stream of hydrogen, give catalysts superior to those known from in art (cf. in particular, Example 11).

The subsequent treatment stages, such as drying and calcination and the rate of heating between the drying stage and the calcination stage, are as important as the observance of certain precipitation conditions, such as the pH value and careful removal of alkalis to values below 0.1% or values below 0.01%. Hence, the essential aspects of the invention are the manufacture of the individual alkali-free catalyst precursor, its drying and the defined temperature rise, at a rate from 1.66 to 3.33C/minute, between drying and subsequent calcination.

The subsequent reduction of the catalyst is in general effected in a stream of hydrogen at temperatures from 300 to 500C and is not a critical factor in the manufacture of the catalyst of the invention.

The catalyst precursor is dried in a narrow temperature range, from 80 to 180C, the range from 90 to 120C being particularly preferred. The drying can be effected in air. 1

The dried catalyst precursor is calcined at temperatures from 300 to 550C. Temperatures from Between the drying stage and the calcination stage, the substance should be heated at a defined rate which is as rapid as possible. The time for heating from the preferred drying temperature to C) to the preferred calcination temperature (340 to 460C) should be not less than 2 hours but not more than 3 hours. From this, the gradients for the temperature rise are calculated to be from l.66C/minute to 3.33C/minute.

The nickel contents of the catalysts can of course not be varied within wide limits since they are essentially determined by the stoichiometry of the catalyst precursor. The nickel contents of the finished catalyst are of the order of 72 to 80% by weight. These values apply to a catalyst produced directly from the catalyst precursor. However, the catalyst precursor can also be precipitated on ceramic supports, such as aluminum oxide (0:, y or 8), hydrated alumina, such as bayerite, boehmite, hydrargillite or their mixtures, titanium dioxide, silica, zirconium dioxide, magnesium oxide and artificial and natural silicates, for example magnesium sil' icate or aluminosilicates. Hydrated aluminas are preferred supports (cf. Examples 2 and 3). To produce these, it is preferred to have the support in aqueous suspension and to precipitate the catalyst precursor on the support. The support and precipitate are separated off and treated further in the way described for the conversion of the catalyst precursor. In this way, any desired nickel content in the finished catalyst is achievable. In general, the nickel contents of supported catalysts are chosen to be from 15 to 80%.

The use of the catalysts of the invention is particularly advantageous for the production of gases containing methane and for the after-treatment of the rich gases produced by naphtha cracking, with the object of producing substitute gases for natural gas (the so-called post-methanization of rich gases). The catalysts of the invention can be used in both the cracking and post methanization stages (where multi-stage postmethanization is involved).

The manufacture of the catalysts of the invention is described in Examples 1, 2 and 3 which follow. Example 4 describes the use of the catalysts in cracking hydrocarbons and Examples 6 and 7 describe the methanization of rich gases.

Example 5 explains how a refinery gas containing carbon monoxide and dioxide can be converted into a gas of higher methane content.

Example 1 1 shows that the catalysts of the invention are superior to the prior art alkalized catalysts according to DAS 1,227,603 and the catalysts according to DAS 1,180,481 (cf. catalyst H and H in all respects. In particular, the suitability for higher space velocities and the higher activity of the catalysts of the invention as compared to alkalized nickel catalysts should be singled out. When the catalysts of the invention are used for the production of gases containing methane, their increased activity has the advantage that the process can be carried out at lower temperatures so that gases with methane contents of the order of 75% by volume are obtained even in one process stage; these gases can then be converted, in a further process stage, with interpolation of a C0 wash, into gases which can be used as substitute gases for natural gas and which conform to the specifications laid down for these gases (CH, 99%, sum of H CO at most 0.1%).

EXAMPLE 1 Catalyst A To precipitate the compound Ni Al (OH) .CO .4- H O, which serves as the catalyst precursor, the following 2M solutions were prepared first:

Solution 1:

13.960 kg 48 moles of Ni(NO .6H O and 6.002 kg 16 moles of Al(NO .9H O were dissolved in sufficient water to produce a total of 32 l of solution.

Solution 2:

7.635 kg 72 moles of sodium carbonate were also dissolved in water and made up to 36 l.

10 l of water were introduced into a stirred kettle. During the precipitation, the pH was measured with an electrode which dipped into the water introduced. Both the above solutions, and the water introduced, were separately heated to 80C. The pH of the water introduced was adjusted to 8.0 by adding a suitable amount of solution 2.

To precipitate the above compound, solutions 1 and 2 were allowed to run separately into the water and a pH value of 7.5 to 8.0 was maintained by regulating the rate of addition, whilst stirring well. After the whole of solution 1 had been added the addition of solution 2 was stopped and the precipitate was stirred for a further 15 minutes at 80C. The resulting precipitate was filtered off and washed until free of alkali. The washed product, which according to X-ray tests proved to be a pure precipitate of Ni Al (OH) .C,O .4I-l O was then dried for 24 hours at 110C, calcined for 20 hours at 450C, mixed with 2% of graphite and pressed to give 5 X 5 mm pills. Analysis showed the following constituents (all the data being in per cent by weight, and based on the oxide contact catalyst): nickel 56.8%, aluminum 9.5% and sodium 0.009%.

EXAMPLE 2 Catalyst B The catalyst B contains a hydrated alumina as the support. This hydrated alumina was obtained by parallel precipitation of sodium aluminate solution and nitric acid within the pH range of 7.5 to 8.0. The precipitate was filtered off, washed until free of alkali and then dried at 200C.

3.720 kg of this support were suspended in l of water in a stirred kettle and the suspension was heated to 80C. The compound Ni Al (OH) .CO .4H O was not precipitated on this suspended support. For this purpose, two solutions were prepared and separately heated to 80C.

Solution 1:

13.960 kg 48 moles of Ni(NO .6H O and 6.002 kg 16 moles of AI(NO .9H O were dissolved in water and made up to 32 l of solution.

Solution 2:

7.635 kg of technical grade sodium carbonate were dissolved in water and made up to 36 l of solution.

The compound Ni Al (OH) .CO .4H O was then precipitated onto the hydrated alumina (namely the support) at pH 7.5 to 8.0, as described in Example 1.

The precipitated product was stirred for a further 15 minutes and the precipitate was then filtered off, washed until free of alkali, dried at 1 10C, calcined for 20 hours at 450C, mixed with 2% of graphite and finally pressed to give 5 X 5 mm pills. Analysis showed that the oxide contact catalyst contained: 39.3% of nickel, 24.1% of aluminum, 0.01% of sodium (all data being in percent by weight).

Catalyst C This catalyst was prepared as described above except that the compound Ni Al (OH) .CO .4H O was precipitated on 4.080 kg of the suspended support and the dry precipitate was calcined at 350C. The resulting (oxide) catalyst contained: 32.5% of nickel, 27.1% of aluminum and 0.009% of sodium (all data being in percent by weight).

Catalyst D This catalyst was prepared like catalyst C, except that the amount of hydrated alumina used to start with was modified. A supported contact catalyst containing: 16.7% of nickel, 38.3% of aluminum and 0.007% of sodium (all data being in percent by weight) was obtained.

Catalyst E This catalyst was prepared like catalyst C and D, except that the compound Ni Al (OI-I) .CO .4H O was precipitated on 6.830 kg of suspended hydrated alumina. The resulting catalyst, in the oxide state, contained: 23.9% of nickel, 31.4% of aluminum and 0.01% of sodium (all data being in percent by weight).

EXAMPLE 3 Catalyst F A hydrated alumina support was prepared by parallel precipitation of an aluminum sulfate solution with ammonia at pH 7.5 The precipitate was filtered off, washed until the sulfate content fell below 0.5% by weight, and dried at 200C.

0.134 kg of this carrier was suspended in 10 l of water in a stirred kettle. The compound Ni Al (OH) .CO .4- H O was precipitated on the hydrated alumina as described in Example 2. The precipitate was filtered off, washed, dried at l 10C, calcined for 20 hours at 350C and finally pressed to give 5 X 5 mm pills. A catalyst containing52.4% of nickel, 12.2% of alumina, 0.006% of sodium (all data being in percent by weight) was obtained.

Catalyst G EXAMPLE 4 Catalyst A 200ml of catalyst A were reduced with hydrogen at 450C under a pressure of 16 atmospheres absolute, in a reaction tube of 24 mm internal diameter, which could be heated externally by means of an aluminum:

block.

A desulfurized naphtha (density: 0.727 g/cm, boiling range 80 to 155C) was vaporized, 2 kg of water being added per 1 kg of naphtha, and the vapor was passed through the catalyst under a pressure of 30 atmospheres absolute and at an entry temperature of 380C. The space velocity was 5 kg of naphtha per liter of catalyst per hour. The temperature of the surrounding aluminum block was kept at 450C. On cooling the cracked gas issuing at 462C from the catalyst layer, the hourly yield was 1.31 kg of water and 1,770 l (S.T.P.) of a dry gas which consisted of 65.9 percent by volume of methane, 23.1 percent by volume of carbon dioxide, 10.6 percent by volume of hydrogen and 0.4 percent by volume of carbon monoxide.

Catalyst B Using catalyst B, with the same feedstock and under the conditions stated above, a cracked gas issuing from the catalyst bed at a temperature of 470C was obtained. On cooling the cracked gas, the hourly yield was 1.31 kg of water and 1,680 l (S.T.P.) of a dry gas which consisted of 64.8% of methane, 23.0% of carbon dioxide, 1 1.7% of hydrogen and 0.5% of carbon monoxide (all data being in percent by volume).

Catalyst F Catalyst F was employed for the cracking of naphtha under the same conditions as catalysts A and B. On cooling the cracked gas, which issued at 468C from the catalyst layer, the hourly yield was 1.30 kg of water and 1,750 l (S.T.P.) of a dry gas which consisted of 65.0% of methane, 23.1% of carbon dioxide, 1 1.4% of hydrogen and 0.5% of carbon monoxide (all data being in percent by volume).

EXAMPLE 5 Catalyst C 200 ml of catalyst C were reduced with hydrogen at 400C and under a pressure of 16 atmospheres absolute in a tubular reactor of 24 mm internal diameter which could be heated externally by means of an aluminum block. 1

A dry gas consisting of: 60.5% of methane, 25.9% of hydrogen, 12.5% of carbon dioxide and 1.1% of carbon monoxide (all data being in percent by volume), was withdrawn from a pressure vessel, heated and mixed with steam in the ratio of 1.07 moles of H 0 per 1 mole of dry gas. The wet gas thus produced, the composition of which corresponds to a cracked gas produced by catalytic steam reforming of a refinery gas, was passed through the catalyst at a pressure of 17 atmospheres absolute and an entry'temperature of 270C, using a space velocity of 6,020 (S.T.P.) of wet gas per liter of catalyst per hour. The temperature of the surrounding aluminum block was kept at 270C. On cooling the wet gas issuing from the catalyst bed at 295C, the hourly yield was 0.56 liter of water and 450 l (S.T.P.) of a dry gas which consisted of 85.5% of methane, 4.3% of hy drogen, 10.2% of carbon dioxide and less than 0.05%

of carbon monoxide (all data being in percent by volume).

Catalyst D Catalyst D was employed, under the same conditions as those described for catalyst C, for the postjmethanization of a refinery cracked gas containing carbon monoxide and carbon dioxide.

On cooling the wet gas issuing at 300C from the catalyst bed, the hourly yield was 0.56 liter of water and 450 l (S.T.P.) ofa dry gas which consisted of 84.9% of methane, 5.0% of hydrogen, 10.1% of carbon dioxide and less than 0.05% of carbon monoxide (all data being in percent by volume).

EXAMPLE 6 450 ml of catalyst A were reduced with hydrogen at 450C under a pressure of 16 atmospheres absolute in a tubular reactor of 24 mm internal diameter which could be heated externally by means of an aluminum block.

A desulfurized naphtha (density: 0.727 g/cm; boiling range to C) was vaporized, with the addition of 2 kg of water per 1 kg of naphtha, and the vapor was passed through the catalyst under a pressure of 30 atmospheres absolute and using an entry temperature of 400C. The space velocity was 0.9 kg of naphtha per liter of catalyst per hour. The temperature of the surrounding aluminum block was kept at 450C. On cooling the cracked gas issuing at 455C from the catalyst bed, the hourly yield was 0.54 kg of water and 700 l (S.T.P.) of a dry gas which consisted of 67.1% of methane, 22.9% of carbon dioxide, 9.6% of hydrogen and 0.4% of carbon monoxide (all data being in percent by volume).

After operating for 24 hours, a second tubular reactor, of 32 mm internal diameter, which could also be heated externally by means of an aluminum block, was connected in series behind the first tubular reactor. This second reactor contained 250 ml of catalyst E which had been first reduced with hydrogen at 350C under a pressure of 16 atmospheres absolute. The water which condensed out after the first tubular reactor was fed in again before the second reactor, vaporized and mixed with the dry gas from the first reactor. The wet gas thus obtained (the composition of which corresponds to that of the wet gas issuing from the catalyst bed of the first reactor) was passed through the catalyst E contained in the second reactor under a pressure of 30 atmospheres absolute and using an entry temperature of 270C. The temperature of the surrounding aluminum block was kept at 270C. On cooling the gas issuing at 305C from the catalyst bed, the hourly yield was 0.56 kg of water and 650 l (S.T.P.) of a dry gas which consisted of 75.6% of methane, 22.8% of carbon dioxide, 1.6% of hydrogen and less than 0.05% of carbon monoxide (all data being in percent by volume).

After 1,040 hours, no change in the composition of the gases produced in the first and second tubular reactors was as yet ascertainable. Whilst continuing to crack the naphtha in the first tubular reactor, the catalyst E in the second tubular reactor was now replaced by the catalyst D: 250 ml of catalyst D were reduced and employed for 1,090 hours under the same conditions as was the catalyst E previously. On cooling the gas issuing at 302C from the catalyst bed, the hourly yield was 0.56 kg of water and 6 60 l (S.T.P.) of a dry gas which consisted of 74.0% of methane, 22.8% of carbon dioxide, 3.2% of hydrogen and less than 0.05% of carbon monoxide (all data being in percent by volume). Since the composition of the gases produced in the first and second tubular reactors continued unchanged, the experiment was discontinued after 1,220 hours.

ample 6 and employed for the steam reforming of naphtha under conditions identical to those of Example 6 with the exception of the space velocity, which was now 2.0 kg of naphtha per liter of catalyst and per hour. On cooling the cracked gas issuing at 475C from the catalyst bed, the hourly yield was 0.53 kg of water and 710 l (S.T.P. of a dry gas which consisted of 66.2% of methane, 22.4% of carbon dioxide, 10.9% of hydrogen and 0.5% of carbon monoxide (all data being in percent by volume).

After 24 hours operation, a second tubular reactor containing 200 ml of catalyst C was connected in series behind the first tubular reactor. The reduction and operation of the catalyst C were effected identically to those described for catalyst E in Example 6. On cooling the gas issuing at 315C from the catalyst bed, the hourly yield was 0.56 kg of water and 6501 (S.T.P.) of a dry gas which consisted of 75.4% of methane, 22.9% of carbon dioxide, 3.2% of hydrogen and less than Duration days ing of hydrocarbons, and the special catalyst (H containing 15% of nickel, described in the cited Printed Application, were compared. 'The table which follows shows the nickel contents, the support of the catalysts mentioned, and the trade names of the catalysts:

The experiments were carried out in a tubular reactor which in each case contained 270 cm of the catalysts mentioned.

The results of the experiments are shown in the table which follows:

Catalyst G1 21 Catalyst G1 40 H DAS 1,180,481 71 by weight of by weight of 72 by weight of naphtha converted naphtha converted naphtha converted 0.05% of carbon monoxide (all data being in percent by volume).

The experiment was discontinued after '520 hours since after this time a change in the composition of the gases produced in the first and second tubular reactors was not yet detectable.

EXAMPLE 8 The comparative experiments were carried out under the conditions indicated in Examples 1 and 2 of German Printed Application No. 1,180,481, namely:

Catalyst temperature: 500C Preheat temperature of the 450C mixture:

Pressure: atmospheres absolute Feedstock: naphtha Steam-naphtha ratio: 2 kg/kg Space velocity: 0.5.kg of naphtha/1 of catalyst hour activated within a very shorttime,

The experiments showthat the process cannot be 9 carried out with the commercially available nickel cracking catalysts since all three catalysts are deactivated very quickly. The experiment with catalyst G1 1 1 was discontinued after 8 days, when the conversion had fallen to merely 11% by weight, and the experiment with catalyst G1 21 was discontinued after 9 days, at a conversion of by weight. Since the experiment with catalyst G1 showed a conversion which was still as much as 61% byweight of the naphtha after 9 days, this experiment was extended to a total of 14 days. After this time, the catalyst was found to be completely deactivated and no longer converted any naphtha. This at the same time shows that the-catalyst activity does not stabilize itself and instead the activity decreases until the catalyst has become completely de- These experiments show nickel catalysts are simplyunsuitable for the process described inthe cited fiPrinted Application. Only the special nickel catalyst on ap u'trelalumina support, manufactured according to DAS 1,180,481, proved suitable, to, a very limited degree the experiment with thiscatalyst was also extended to 14 days. After this time, the catalyst still converted benzine completely. However, with a commercial space velocity of 1. kg of naphtha per liter of a catalyst per hour, this catalyst also no longer permits complete cracking of thenaphtha (compare also Example (With regard to the method used for the experiments, it should be noted that the gas chromatography method was capable of detecting 1 ppm of higher hydrocarbons.)

EXAMPLE 9 Experimental conditions: Catalyst temperature (maximum temperature of aluminum block) 470C Preheat temperature of the mixture 420C Pressure 30 atmospheres Feedstock naphtha Steam/naphtha ratio 2 kg/k g 1 kg of naphtha/1 of catalyst hour Space velocity Time at which unchanged Catalyst according Nickel content naphtha is found to DAS 1,180,481 by weight in the output l H 15 from the start 2 H, 24.9 from the start 3 H, 51.2 after 7 hours EXAMPLE 1O Catalyst 1 A catalyst was produced by precipitation in accordance with the instructions of German Printed Application No. 1,227,603. The precipitate was filtered off, suspended 6 times in hot water, alkalized, dried at 110C and calcined at 450C. The calcined material was then mixed with 2% of graphite and pressed to give 5 X 5 mm tablets. Analysis of the oxide catalyst showed: 25.0% of nickel, 65.4% of A1 0 3.05% of potassium (all data being in percent by weight).

Catalyst K The catalyst was prepared analogously to Example 6 of German Printed Application No. 1,227,603. The analysis of the oxide catalyst showed: 61.4% of nickel, 19.5% of A1 0 1.31% of potassium (all data being in percent by weight).

EXAMPLE 1 1 To compare the activity of catalysts H H 1, K and A, all were tested under the following conditions:

The experiments were carried out in the same tubular reactor, which had an internal width of 24 mm and was surrounded by an aluminum block. The naphtha-steam mixture entered at 380C. A desulfurized naphtha of density 0.727 g/cm and boiling range to C was exployed. The space velocity was 5 kg of naphtha per liter of catalyst per hour, using a weight ratio of 11 0/- hydrocarbon 2.0 and a pressure of 30 atmospheres absolute. The temperature of the surrounding aluminum block was 450.

The parameter measured in order to compare the activity was the time in hours after which quantities of unconverted higher hydrocarbons first occurred in the cracked gas. Results are shown in the table and represented in the figure:

1. A process for the manufacture of methane by conversion of a gas which contains carbon monoxide, carbon dioxide and hydrogen and which has been preheated to a temperature of from 200 to 300C, at superatmospheric pressure in the presence of a nickel catalyst, wherein the catalyst is manufactured by precipitating the compound Ni Al (OH) .CO .4l-l O from aqueous solution, drying it at a temperature of from 80 to 180C, calcining it at a temperature of from 300 to 550C and subsequently reducing it in a stream of hydrogen, with the proviso that between the drying stage and the calcination stage the temperature is raised at a rate in the range from 1.66/minute to 3.33C/minute.

2. A process of the manufacture of methane by conversion of a gas which contains carbon monoxide, carbon dioxide and hydrogen and which has been preheated to a temperature of from 200 to 300C, at superatmospheric pressure in the presence of a nickel catalyst, wherein the catalyst is manufactured by precipitating the compound Ni A1 (Ol-l) .CO .4l-1 O onto a support in aqueous suspension, separating off the support together with the precipitate, drying the product at a temperature of from 80 to 180C, calcining it at a temperature of from 300 to 550C and subsequently reducing it in a stream of hydrogen, with the proviso that between the drying stage and the calcination stage the temperature is raised at a rate of from 1.66/minute to 3.33C/minute. 

1. A PROCESS FOR THE MANUFACTURE OF METHANE BY CONVERSION OF A GAS WHICH CONTAINS CARBON MONOXIDE, CARBON DIOXIDE AND HYDROGEN AND WHICH HAS BEEN PREHEATED TO A TEMPERATURE OF FROM 200* TO 300*C, AT SUPERATMOSPHERIC PRESSURE IN THE PRESENCE OF A NICKEL CATALYST, WHEREIN THE CATALYST IS MANUFACTURED BY PRECIPITATING THE COMPOUND NI6AL2(OH)16,CO3,4H2O FROM AQUEOUS SOLUTION, DRYING IT AT A TEMPERATURE OF FROM 80* TO 180*C, CALCINING IT AT A TEMPERATURE OF FROM 300* TO 55*C AND SUBSEQUENTLY REDUCING IT IN A STREAM OF HYDROGEN, WITH THE PROVISO THAT BETWEEN THE DRYING STAGE AND THE CALCINATION STAGE THE TEMPERATURE IS RAISED AT A RATE IN THE RANGE FROM 1.66*/MINUTE TO 3.33*C/MINUTE.
 2. A process of the manufacture of methane by conversion of a gas which contains carbon monoxide, carbon dioxide and hydrogen and which has been preheated to a temperature of from 200* to 300*C, at superatmospheric pressure in the presence of a nickel catalyst, wherein the catalyst is manufactured by precipitating the compound Ni6Al2(OH)16.CO3.4H2O onto a support in aqueous suspension, separating off the support together with the precipitate, drying the product at a temperature of from 80* to 180*C, calcining it at a temperature of from 300* to 550*C and subsequently reducing it in a stream of hydrogen, with the proviso that between the drying stage and the calcination stage the temperature is raised at a rate of from 1.66*/minute to 3.33*C/minute. 